Zinc chloride



Patented .luiy 18, 1939 UNITE SATES ATENT oric ZINC CHLORIDE.

de Nemours &

Comp corporation of Delaw any, Wilmington, Del., a are No Drawing. Application November 11, 1937, Serial No. 174,056

2 Claims.

This invention relates to zinc chloride and has for its object retarding or preventing turbidity in zinc chloride solutions.

When commercial zinc chloride is dissolved in water a turbid or cloudy solution results, due to the formation of basic zinc chloride. This turbidity may appear immediately or after a period of several days, depending upon the concentration of the solution, the more dilute solutions favoring turbidity. Thus when normally clear concentrated solutions are diluted the solutions become immediately turbid or cloudy. The same phenomenon occurs with the purer grades of zinc chloride. The purer solutions, however, will stand longer before turbidity appears or with the same period of standing diluter solutions may be made without becoming turbid.

Turbidity formation is particularly pronounced when the zinc chloride has passed thru the dry state, as for example, in the production of granular zinc chloride. It is consequently a further object of this invention to prepare granulated zinc chloride in such a form that it may be readily diluted without forming turbid solutions.

We have now found that turbidity formation in zinc chloride solutions is delayed by the presence of a small amount of citric or tartaric acid. Solutions prepared from granulated zinc chloride containing citric or tartaric acid or concentrated solutions prepared from granulated zinc chloride to which citric or tartaric acid are added behave in a manner similar to or even better than corresponding solutions prepared from a purer grade of zinc chloride.

In the following example, which may be considered as illustrative of the invention, 50 per cent solutions were diluted until they contained about 16.6 per cent zinc chloride. Comparison was made of chemically pure granular zinc chloride, commercial granular zinc chloride, commercial granular zinc chloride containing 0.5 per cent citric acid, and commercial granular zinc chloride containing one .per cent tartaric acid. The following table clearly illustrates the inhibiting eflect of citric acid and tartaric acid on turbidity formation:

Table Rum Commercial zinc chloride Time zinc h N o addi- Citric acid Tartaric n 9 tion 0.5% acid 1% When diluted C S to M O B After standing 15 minutes S to M C 8 After standing 1 hour.-. M M C S After standing 24 hours. ME MH F B After standing 6 days ME ME VS R The notations used above are as follows: C-clear solution.

F-faint turbiditynoticeable only in good light.

VSvery slight turbidity.

Sslight turbidity.

Mmedium turbiditydoes not readily settle.

MHmedium to heavy turbiditysmall amount of white precipitate.

From the foregoing it is apparent that while the commercial zinc chloride is definitely inferior to the pure zinc chloride, the commercial zinc chloride treated with citric acid is definitely superior both with respect to turbidity formation on dilution and on standing. The commercial zinc chloride containing tartaric acid while not quite so effective against turbidity formation on dilution is more resistant to an increase in turbidity on standing.

While we have disclosed our invention with reference to certain specific conditions, it is to be understood that numerous variations may be made without departing from the spirit of the invention which in its broader aspect contemplates the use of citric and tartaric acids for delaying, retarding, inhibiting, or preventing turbidity formation in zinc chloridesolutions.

We claim:

1. A composition of matter consisting essentially of zinc chloride and av small amount of at least one hydroxy carboxylic acid selected from the group consisting of citric acid and tartaric acid.

2. Granular zinc chloride containing in the order of 0.5 to 1 per cent of at least one hydroxy carboxylic acid selected from the group consisting of citric acid and tartaric acid.

RAYMOND J. KEPFER. ARTHUR K. 'IELFER. 

